Image sensor devices are widely used in various imaging applications and products, such as digital still cameras or mobile phone camera applications. These devices utilize an array of sensor elements (pixels) in a substrate. The pixels may be photodiodes or other photosensitive elements that are adapted to absorb light projected toward the substrate and convert the sensed light into electrical signals. To receive more light, it is advantageous to increase the number of the pixels in the image sensor devices.
The ever-shrinking geometry size brings challenges to image sensor device fabrication. For example, the fabrication process may require photoresist masks with high aspect ratio to produce pixels that are micron or sub-micron in size. However, photoresist masks with high aspect ratio are more prone to the effects of capillary forces. These effects are exacerbated as the aspect ratio of the mask increase and/or as the pitch decreases. As a result, photoresist masks may collapse, for example, due to the pulling effect of capillary forces between adjacent photoresist masks.